Solve for array of values for cos and sin functions returning [0x1 sym]

Hello,

I am having problems with using an array in a cosine function, I have replicated the problem in a much simpler example code:

clear all
c = 1:1:10;
syms x  y
a = x^2 + sind(c) -y == 3;
b = x - cosd(c) +y ==5;
solve([a b], [x y])
ans = 
  struct with fields:
    x: [0×1 sym]
    y: [0×1 sym]

I am expecting this to return an array of each iteration of sind(c), or some way of doing so, but instead I just get nothing at all.

I thought I had my head around Matlab but this one has stumped me, also I'm a first time user of Matlab forums so I hope the formatting has come out OK, I googled how and just found posts about how annoying it is explaining to forum newbies to format your code :P

[infinity]

Hello,

Why do you dupplicate "a" like this

a = x^2 + c -y == 3;
a = x^2 + sind(c) -y == 3;

what is the first equation exactly? I guess the second one is "b".

[Dylan Gannan]

I have edited it, cheers.

My question is how do I solve for each array value so that I can plot its output.

I am plotting the position of a link in a walking robot mechanism for a 360 degree rotation of it's crank. So one of my theta values is going to have 1:1:360. I made that question above to simplify and define my error.

[infinity]

Have you tried @Alex Mcaulley's solution?

Answer 1

[Alex Mcaulley]

One way:

syms x y c
a = x^2 + c - y == 3; % function a is overwritten in the next line!
a = x^2 + sin(c*pi/180) - y == 3; %c in degrees
b = x - cos(c*pi/180) + y == 5;
res = solve([a b], [x y]);
resx = double(subs(res.x,c,1:1:10));
resy = double(subs(res.y,c,1:1:10));